Geology and age of the Kemess porphyry copper-molybdenum deposit, north-central British Columbia

CIM Bulletin, Vol. 73, No. 821, 1980

R.M. CANN and C.I. GODWIN, Department of Geological Sciences, The University of British Columbia, Vancouver, B.C.

Abstract
The Kemess porphyry copper-molybdenum deposit occurs in the Intermontane Belt of north-central British Columbia. The deposit is in andesitic to basaltic flows and tuffs which may be correlated with the Savage Mountain Formation of the Upper Triassic Takla Group. Most known chalcopyrite and molybdenite is associated closely with a 500-m-diameter zone of intense quartz-sericite-pyrite alteration. A zone of supergene enrichment, up to 30 m thick, underlies a leached capping about 20 m thick. The age of mineralization and the surrounding granodiorite and quartz monzonite pluton is Early Jurassic. K-Ar and Rb-Sr analyses indicate that the mineralization and alteration is slightly younger (182±6 Ma) than the granitic intrusion (K-Ar: about 205±6 Ma; Rb-Sr: 190 ±4 Ma). The low 87Sr86Sr initial ratio for the granodiorite is typical of plutons in the Intermontane Belt.